It is for some, but not many. By charging a higher rate they eleminate the potential of dealing with tire kickers and time wasters. But by doing so they also raise the bar, at 300 an hour the level of service expected is equally higher as well as the expectation for no drama, games or excuses. If they deliver on both looks and service then their fee structure could work, all be it with a much smaller client base. It's possible they may adjust their rates accordingly once the market determines the fair value.
Worth notiing that their ads on the pink board state 250/hr in Ottawa, which is more in line with this city. Perhaps in touring cities they can get higher rates, I think the going rate in Fort Mac is $350 for example.